The basic problem in timepieces including date and moon phase displays is to furnish the user rapid correction means of both displays in order to mitigate the consequences either of an interruption in the current supply in the case of an electromechanical timepiece, or failure to operate the winding mechanism for timepieces of the purely mechanical type.
Thus, a first method for changing the date and moon phase display consists in employing the winding stem in the position and function of time setting for the hours and minutes indicating means, then to cause rotation of such indicating means as many times as it is necessary to pass several days, indeed several weeks.
It is well understood that this method is very long since the switching of the mechanisms for displaying respectively the dates and moon phases is repeated only every 24 hours. Thus, such method is very tedious and even laborious.
It is thus necessary to provide the user other means which permit him to correct rapidly both displays without necessarily passing through operation of the hours and minutes indicating means.
Furthermore, it has always been desired that during the normal operation of the movement, passage from one date to another and the visible evolution of the moon phases take place instantaneously. This has given rise to numerous solutions, the most utilized of which are known under the name of jumper mechanisms. Hence, the respective wheels for the dates and moon phases are constituted by star wheels, that is to say, by discs having triangular teeth the driving of which must be effected by a device which is not in constant mesh with such stars but which, over a predetermined period, namely every 24 hours, effects successive or simultaneous operation of such two stars.
This driving d&vice may be constituted for instance by a pin which is fixed to a wheel and which meshes with a setting wheel of the horometric movement.
However, it is understood that when such jumper mechanism is combined with a rapid correction system, one of the pins or the driving pin of the stars may be in mesh, for instance with the date star, while at the same moment the user modifies the displayed date.
The time lapse during which the pin is in mesh with a corresponding star is relatively long so that this probability is far from being negligible.
Timepieces generally cannot withstand a reversible operation of the stars and there would occur in such case blockage or breakage of one of the constituents.
Swiss patent CH Nr. 4542 dating from 1891 proposes an improved date mechanism which addresses this problem.
Such mechanism includes in a standard manner a date star for displaying dates as well as a lunar month star for displaying moon phases. These two stars are driven in a successive manner by a unique driving device which is connected to a setting wheel of the horometric movement and which is equipped on its face with a lifting piece subjected to the action of a spring. Such lifting piece comes into mesh sometimes with the date star, sometimes with the moon phase star in order to bring about their advance in combination with jumper springs.
Furthermore, such date mechanism includes corrector devices, namely elongated levers pivotally mounted on the base plate of the movement, a first free end of which is brought to operate one of the corresponding stars, while a second end is arranged outside the watch case. Thus, the user, in pressing these corrector devices, operates directly on the date and lunar month stars and he may thus change the display in a corresponding manner. Furthermore, since the lifting piece of the driving device is elastically coupled to the wheel which bears it, such lifting piece through a click phenomenon, withstands the operation of these return devices without passing the effect back to the wheel, thus to the other constituents of the movement.
Nevertheless, such a mechanism includes numerous disadvantages.
Effectively, the use of correctors initially requires lateral openings in the case which is thus difficult to render moisture-tight also not forgetting that such correctors are generally not particularly aesthetic.
Furthermore, such correctors are of a complex form and being relatively long, necessitate for their displacement considerable travel and thus considerable space. Additionally, their manufacture and assembly increase substantially the cost price of the timepieces.
It will also be noted that in this patent, the two stars respectively for the date and moon phases are greatly separated from one another so that they also occupy considerable space. It is thus understood that such an arrangement is initially costly, but also that it may not be applied to fabrication of a timepiece of small dimensions which above all should be compact.
Additionally, such mechanism may only with difficulty equip a timepiece in which the date star is centered on the movement since in such a case the moon phase star must be placed still more towards the exterior of the movement, being given that the respective axes of the date star, the moon phase star and the driving device are arranged on a straight line.
Furthermore, there is described in the work "Les montres calendriers modernes" of B. Humbert, published in 1953 in the editions of the "Journal Suisse d'Horlogerie" pages 100 and 101, FIG. 159, a mechanism in which the date star with 31 teeth is centered on the horometric movement in a manner coaxial to the hours and minutes indicators. The day star bears a hand which advances in coincidence with the days of the week indication marked on the outer periphery of the dial.
In this caliber, the space requirement has been substantially optimized by the use of a single driving device, as in the preceding mechanism, but having a conception completely special. Effectively, such driving device includes a cam freely mounted on a wheel which is driven by the horometric movement. On such cam are arranged fingers, one being intended to drive successively the date star and the other, that of the moon phases.
Such cam is driven by the wheel to which it is fixed through a pin housed in a partial clearance arranged on the periphery of the cam. In such clearance are formed two shoulders adapted to butt against the pin.
Thus, when one wishes rapid correction of one of the display stars, the cam may separate from the pin which pushes it since such cam is freely mounted relative to the driving wheel.
Nevertheless, this conception is relatively complex since it necessitates difficult machining operations and costly assembly and adjustment operations of the elements among themselves.
Thus, here again it is understood that it is impossible with this calibre to offer very small dimensions at the lowest possible price.
Thus, the present invention has as purpose to overcome these difficulties in proposing a timepiece of the mechanical and/or electromechanical type and particularly a timepiece furnishing displays, in particular of dates and moon phases which are of small dimensions, obtainable at very low cost and which includes rapid correction means for such displays which are simple and do not change the compactness of the assembly.